<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <script type="text/javascript" src="../js/vue.js"></script>
</head>
<body>
<!-- 容器 -->
<div id="root">
    姓：<input type="text" v-model="firstname"><br>
    名：<input type="text" v-model="lastname"><br>
    {{allname}}<br>
</div>
<script type="text/javascript">
    new Vue({
        el: '#root',
        data:{
            firstname:'张',
            lastname:'三',
            allname:'张-三'
        },
        watch:{
            firstname(newVal,oldVal){
                setTimeout(()=>{
                    this.allname=newVal+'-'+this.lastname;
                },1000);
            },
            lastname(newVal,oldVal){
                this.allname=this.firstname+'-'+newVal;
            }
        }
    })
</script>
</body>
</html>